Understanding the Use Case Model
• Purpose of Use Case Model
– Focus on the target rather than the means of getting to the target (key functions) – Focus on the goal of process – Focus on who will use the system? And what will they use it to do for them?

• Resources of the Use Case Model
– Use Case Diagram: the graphical modeling show the communication between actor and use case – Use Case Narrative: describe each use case as the text description – Use Case Scenario: show the path of process flow for each use case to get the goal. Each path will illustrate in activity diagram.
Chapter 3 2

Prepared by: IECH Setha

1

User placed outside the system boundary. system (other system).Elements
– Actor: is the people.
<<Actor>> Actor Name
Actor People System or Device
• Example
Chapter 3
4
Prepared by: IECH Setha
2
.Royal University of Law and Economics
27/11/2011
Building Use Case Diagram
• Elements of Use Case Diagram
There are 6 important elements – System: the boundary of system being studied
– Example
Chapter 3
3
Building Use Case Diagram . and devices that communicate with system.

Use case placed inside the system boundary.Royal University of Law and Economics
27/11/2011
Building Use Case Diagram .
• Example
Chapter 3
6
Prepared by: IECH Setha
3
. The solid line that is connected from actor to use case called association.Elements
– Association: the communication of actor and use case.
• Example
Chapter 3
5
Building Use Case Diagram .Elements
– Use Case: referred to the functionalities (key function) or features of system and fulfill by user.

The arrow forward from use case 1 to use case 2.Elements
«uses» Use Case 1 Use Case 2
«extends» Use Case 1 Use Case 2
• Example
Chapter 3
8
Prepared by: IECH Setha
4
.Elements
• Dependency: the relationship between use case and use case. • <<extends>> dependency: the relationship between use case 1 and use case 2 in which use case 1 might need the helps from use case 2. The arrow backward from use case 2 to use case 1. some time we use <<use>> dependency instead of <<include>> dependency.Royal University of Law and Economics
27/11/2011
Building Use Case Diagram .
Chapter 3 7
Building Use Case Diagram . There are two main dependency in use case diagram.
• <<include>> dependency: the relationship between use case 1 and use case 2 in which use case 1 always need the help from use case 2. that is <<include>> dependency and <<extends>> dependency. Note that.

Below is talking about use case 2 inherits from use case 1.Royal University of Law and Economics
27/11/2011
Building Use Case Diagram .Elements
• Example
Chapter 3
10
Prepared by: IECH Setha
5
.
Chapter 3
9
Building Use Case Diagram .Elements
– Generalization: the relationship between actor and actor or the relationship between use case and use case.

Steps
• Set the context of the target system • Identify the actors
– Who will be the primary actor for the system? – Who will be supported? – Who will maintain. administrate the system? – Which other system does it interact with? – Who or what has an interest in the results that the system produces?
Chapter 3
11
Building Use Case Diagram .Steps
• Identify the use cases and associations between actors and use cases – What does the system produce for the actors? (Output)
– What does the actor help the system do? (input)
• Evaluate the actors and use cases to find opportunities for refinement
– Merge Actor – Rename Actor or Use Case – Split Actor
• Evaluate the Use Cases for dependencies • Evaluate the actors and Use Cases for generalization
Chapter 3 12
Prepared by: IECH Setha
6
.Royal University of Law and Economics
27/11/2011
Building Use Case Diagram .

Royal University of Law and Economics
27/11/2011
Example of Building Use Case Diagram (POS)
• Example 1: Point of Sale System in Minimart
(Study the system requirements by using Use Case Model)
– Set context of system
• This POS system will use in a Minimart at the front desk in order to manage sale transactions. This system will communicate with Inventory Control System in order to get stock quantity and update stock balance automatically. We have one cashier using the system to print receipt for customers when they buy products. Seller. Manager • System: Inventory Control System
– Identify use case and define association between actors (users) and use case
• Key functions for cashier or seller
– Create Receipt – Print Receipt
Chapter 3 14
Prepared by: IECH Setha
7
. System Admin. we can produce sale reports effectively and efficiently. From this system.
Chapter 3
13
Example of Building Use Case Diagram (POS)
– Identify actors: who will use the system?
• People: Cashier.

cashier and seller should emerge together because we have only one in the system. Also the manager act as the system admin.Royal University of Law and Economics
27/11/2011
Example of Building Use Case Diagram (POS)
– Evaluate the actors and use cases to find opportunities for refinement (if exists): In this case.
– Evaluate the actors and Use Cases for generalization: N/A
Chapter 3 18
Prepared by: IECH Setha
9
.
Chapter 3
17
Example of Building Use Case Diagram (POS)
– Evaluate the Use Cases for dependencies: just want to find the related use cases.

Chapter 3 20
Prepared by: IECH Setha
10
. The way to calculate stock balance we need some relevant transactions such as enter product import. because if there is not enough stock then POS system cannot process sale transactions. The purpose of this system is to calculate stock balance.Royal University of Law and Economics
27/11/2011
Example of Building Use Case Diagram (POS)
– POS System Use Case Diagram
POS System
«uses» Create Receipt «uses» Get product list
«uses» «uses» Update stock balance
Cashier Print Receipt Change product price
Get stock quantity
<<actor>> Inventory Control System
Backup database «uses» View audit trail
Restore database Setup user System admin Define user privileges «extends»
Produce sale reports
Chapter 3
19
Example of Building Use Case Diagram
• Example 2: Inventory Control System in Minimart
– Context: Inventory Control System will integrate with Point of Sale System which is described in Example 1 above. It is importance when sale transactions created. make purchase return and create stock adjustment.

Royal University of Law and Economics
27/11/2011
Example of Building Use Case Diagram – Inventory Control System
Chapter 3
23
Example of Building Use Case Diagram – Inventory Control System
– Evaluate the Use Cases for dependencies: just want to find the related use cases
– Evaluate the actors and Use Cases for generalization
Chapter 3
24
Prepared by: IECH Setha
12
.

Until the user indicates that he/she is done on entering product code requested from customer .If sale quantity greater than stock quantity then System show message “Not enough stock.If Amount Paid less than Total Amount then System show message “Pay amount not enough.The user may cancel (click button close without saving cancel from customer) .Data save to database correctly
Use Case Termination
Post-condition
Chapter 3
26
Prepared by: IECH Setha
13
.System request product quantity from user . • Use Case Initiation: describe how to start a Use Case.User enter product code . • Process or Dialog: describe how the user interacts with the system during execution of the use case.User enter amount paid after requested from customer .The use case may timeout by system stuck .The system waiting user to enter product code .System show product name.System show total and request user to enter pay amount . Elements of use case narrative are
• Pre-conditions: the conditions that we must pass before starting to process use case.” User re-enter pay amount again and re-check by system . Me 13/12/08 N/A This use case start when customer request to buy goods . • Post-conditions: define the state of the system that must be true when the use case ends. • Use Case Termination: define different mechanisms that can cause the Use Case to stop execution.else User continue enter product code .User enter product quantity .System get stock qty of product (from Check Stock Qty Use Case) .else System show pay back amount System print receipt . price .
Chapter 3 25
Use Case Narrative
– Example: Use Case: Create Receipt (in POS System)
Field Name Name Number Author Last update Pre-conditions Use Case Initiation Dialog Field Description Create Receipt 1 Mr.Royal University of Law and Economics
27/11/2011
Use Case Narrative
– Use Case Narrative is a text description of each use case (one-by-one) that talking about communication between use case and user (actor).The user can indicate that he/she is done .” User re-enter product qty again and system re-check .